This invention relates to vehicles that derive motion from one or more flapping wings.
Since the advent of controlled heavier-than-air flight in the early 1900's, development of aircraft has focussed primarily on fixed-wing and rotary wing technologies. Fixed-wing technologies are typified by commercial, military and pleasure airplanes, in which thrust is generated by a propeller or jet engine and the forward movement of an airfoil through the atmosphere creates lift. Rotary-wing technologies are employed in helicopters, in which lift is generated by pushing air downward with rotating rotor blades. Each of these technologies has its advantages and limitations.
Fixed-wing technologies, for example, permit very high forward velocities and maneuverability. However, both lift and maneuverability depend on the forward motion of the aircraft. Vertical short take-offs or landings (VSTOL), hovering and other maneuvers cannot be accomplished using fixed-wing technology alone. Similarly, turns cannot be executed without rolling the fuselage, and very sharp angle turns cannot be accomplished. Rotary-wing technologies offer improved VSTOL and hovering ability, but their forward and sideways velocities usually are limited, as is their ability to turn. In addition, rotary-wing aircraft often respond poorly to wind gusts.
Hybridized vehicles incorporate fixed-wing and rotary wing technologies to create a combined lift-thrust force. These vehicles have shown limited improvements in maneuverability and versatility compared to fixed-wing and rotary wing vehicles.
A third approach to heavier-than-air flight employs flapping wings to generate a combined lift-thrust force. In principle, flapping wing technology offers the possibility of creating versatile flight vehicles that can combine and in some cases exceed the performance advantages of fixed-wing and rotary-wing technologies. In particular, flapping wing technology offers the possibility of providing improved maneuverability compared to even rotary-wing technologies. Vehicles employing flapping wing technologies are referred to as "ornithopters".
Unfortunately, very few ornithopters have succeeded in flying. In 1929, Lippisch developed a human-powered ornithopter that achieved non-sustained flight. In 1986, MacCready et al. developed an ornithopter modeled on a pterosaur, an extinct flying reptile. That ornithopter was winch launched and could not sustain flight for an extended duration. More recently, Harris and DeLaurier developed an ornithopter that was capable of sustained flight. In addition, various toys have been developed that employ flapping wing technology to fly, including that described in U.S. Pat. No. 4,729,728 to Van Ruymbeke.
Unfortunately, even those previous ornithopters that were capable of flight were very limited in their maneuverability. These ornithopters operated by flapping wings only in a single trajectory, i.e., in an up and down motion. Thus, the aerodynamic force developed by the flapping wings over the course of a series of "beats" was fixed in a fixed (relative to the vehicle), substantially vertical plane. To develop lift, these ornithopters mimicked conventional fixed wing aircraft in that in all cases lift was achieved by creating airflow past an airfoil due to the forward motion of the vehicle as a whole. Thus, these ornithopters suffered from the same maneuverability limitations as conventional fixed-wing aircraft.
In an analogous way, conventional and submersible watercraft, spacecraft and satellites also are limited in their maneuverability due to the design of their propulsion systems.
It would be desirable to provide a wing-drive mechanism, that can affect more than one wing trajectory, thereby generating a force vector over the course of a "beat" or series of "beats" which has an arbitrary but predetermined and changeable magnitude and/or direction. It would also be desirable to provide a method of controlling a wing-drive mechanism that can affect more than one wing trajectories. It would further be desirable to provide a vehicle having at least one flapping drive wing that can affect multiple wing trajectory. It would further be desirable to provide a method for improved control of the motion of an ornithopter or other vehicle as a whole.